The Effect Of White Noise Exposure At 100dB SPL On Auditory Nerve Myelination In Mouse Cochleae

Objective:To investigate whether exposure to white noise at 100 dB SPL for 2 hours causes myelin damage in the peripheral fibers of ganglion neurons of adult C57BL/6J mice.Methods:A total of 24 adult C57BL/6J mice were randomly divided into 4 groups:the control(without the noise treatment),P0(immediately after the noise treatment),P7(7 days after the treatment),and P14(14 days after the treatment).ABR thresholds were measured at above defined time points,and then the cochleae were harvested for assessment of neuronal integrity using immunostaining and TEM observations.Results:At P0,a significant elevation in the ABR thresholds was found at all the tested frequencies(including the click-evoked threshold)as compared with the control group(P<0.05),and the most significant elevation in ABR thresholds appeared at the 8 kHz,16 kHz,and 32 kHz(P<0.01).At P7,the significant elevation of ABR thresholds was seen only at 32 kHz(P<0.05),and there was no significant difference at the all tested frequencies(included click)at P14(P>0.05).No detectable sign of demyelination was found in the immunostained samples.Moreover,TEM observations showed a normal ultrastructure in all groups.Conclusions:While exposure to noise at 100dB SPL for 2 hours causes a temporary threshold shift,it did not result in disruption of the auditory nerve myelination in adult C57BL/6J mice.